Interpretive Summary: The tomato is the second largest vegetable crop in dollar value in the U.S. with a fresh market value of $1.6 billion in 2005. Using chemical and sensory analyses, the nineteen most important odorants responsible for fresh tomato flavor were identified and quantified. It was shown that the differences between highly appetizing and less appetizing tomatoes were due to variations in the concentrations of certain flavor compounds. Higher amounts of the (E,E)- and (E,Z)-2,4-decadienal isomers and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (Furaneol®) had a positive influence on preference, whereas high concentrations of methional, phenylacetaldehyde, 2-phenylethanol or 2-isobutylthiazole had a negative influence. This fundamental knowledge will help plant breeders and growers to select cultivars with the highest consumer preference.

Technical Abstract:
Three tasty (BR-139, FA-624 and FA-612) and two less tasty (R 144 and R 175) fresh greenhouse tomato cultivars, which significantly differ in their flavor profiles, were screened for potent odorants using aroma extract dilution analysis (AEDA). Based on AEDA results, 19 volatiles were selected for quantification in those five cultivars using gas chromatography/mass spectrometry (GC/MS). Odor units (ratio of the concentration of an odorant and its odor threshold) were calculated for all key odorants in each tomato cultivar and compared between the highly accepted and less accepted cultivars for differences. Compounds such as 1-penten-3-one, (E,E)- and (E,Z)-2,4-decadienal and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (Furaneol) had higher odor units in the more preferred cultivars, while methional, phenylacetaldehyde, 2-phenylethanol or 2-isobutylthiazole had higher odor units in the less preferred cultivars. Simulation of the odor of the selected tomato cultivars by preparation of aroma models and comparison with the corresponding real samples confirmed that all important fresh tomato odorants were identified, their concentrations were determined correctly in all five cultivars and that differences in concentration, especially of the compounds mentioned above, make it possible to distinguish between them and are responsible for the differential preference. Sensory and statistical evaluations revealed no major differences in odor between the tomato samples and their corresponding aroma models. To help elucidate formation pathways of key odorants, labeled precursors were added to tomatoes. Biogenesis of cis- and trans-4,5-epoxy-(E)-2-decenals from linoleic acid and methional from methionine was confirmed.